# All Questions

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41 views

### OpenFOAM and CFDEM on GPU

I have a simulation project written for OpenFOAM and CFDEM and would like to find an alternative to run it on GPU since raising the number of cores already provided a promising speed up and ...
76 views

### Computer build for scientific or big data computing [closed]

I'm wanting to build a computer for scientific or big data computing (Python, Fortran, Matlab) and I was hoping to get some advice on the type of processor, memory, graphics, etc I would need. I ...
34 views

### contact mechanics in COMSOL

It seems to be very hard to use comsol to solve contact mechanics problems. Parametric solvers seem to be the only working solvers, followed by Static solvers. Transient solvers never work. Are these ...
51 views

### what does “D = diag(W.1)” means?

, what does “D = diag(W.1)” means?on page #2, just below equation (6) PFA screenshot and here is the link of the paper - original paper
33 views

### Algorithm to join hexahedra and obtain outline volume

I would like to join several hexahedra and obtain an outline volume. First, I started with 2D implementation. In 2D, there are non-intersecting quadrangles which always touch each other as shown in ...
66 views

### How to read data from simply formatted text file (c++)?

Mesh information like points, faces and cells is to be stored into separate files: e.g. for points file: # points data: x y z N_Points 100 x1 y1 z1 x2 y2 z2 ... cell file: # cells data: ...
91 views

### How to optimize sampling for parameter estimation

I have a computer model with a number of parameters that need to be calibrated based on experimental results. It's also important to understand the sensitivity of the results to each parameter ...
66 views

### Fast algorithm for computing cofactor matrix

I wonder if there is a fast algorithm, say ($\mathcal O(n^3)$) for computing the cofactor matrix (or conjugate matrix) of an $N\times N$ square matrix. And yes, one could first compute its determinant ...
88 views

### Original paper on the augmented Lagrangian method in FEM

I am writing a paper in which I want to cite the earliest reference to the augmented Lagrangian method in FEM. For the pure Lagrangian method in FEM, the classical work of Babuška [1] is the original ...
76 views

### How to perform local sensitivity analysis for partial differential equations

I am looking for a way to do local sensitivity analysis for PDEs, preferably in Python. I get the impression that discretizing the equation then treating it as an ODE could work; however, would that ...
83 views

### Bilinear interpolation for large grids

I need to make a bilinear interpolation of a function $Y(i,j)$ tabulated on a $100\times 100$ grid. I tried to do it with the Fortran polin2.f and ...
31 views

### difference between PLSA and LDA

What is the difference between Probabilistic Latent Semantic Analysis(pLSA) and Latent Dirichlet Allocation (LDA)?
133 views

### calculation of the right hand side of DG FEM (with code)

I got stuck with Hestaven/Warburton's dG-FEM Matlab code. Starting with the file AdvecRHS1D.m, we see in line 11 ...
48 views

### Null space for smoothed aggregation algebraic multigrid

I do not really get the point of null space usage for creating the prolongation operator for smoothed aggregation algebraic multigrid. I know what the null space is per definition and I know that the ...
31 views

### Draw contour line to represent multiple contours

I have 5 data sets, each includes multiple scatter points. If I use the geom_path function in R, I could obtain 5 contours like the following graph shows. Those five contours are annotated outlines ...
30 views

### How to implement the Impulse Based Dynamics for the rigid body dynamics simulation?

I am having hard time learning the method of impulse based dynamics developed by Mirtich for rigid body dynamics simulation. Please help me out if any body has any example code(algorithm) of it. ...
89 views

14 views

### Why I am not able to generate Levy distribution using inverse transform method on MATLAB?

I am trying to generate random numbers using Levy distribution in MATLAB. I am using the inverse transform method to generate random numbers and then plot its histogram for pdf estimation. Then I ...
68 views

56 views

### What are the differences between these different forms of equation?

What are the differences between Conservative differential form, Non-conservative differential form, Conservative Integral form and Non-conservative integral form of differential equations? I know ...
48 views

132 views

### Why my parallel code using MPI is much slower than the serial one?

I know that is not the first time someone asks this question but I'm really confused.I'm new to MPI, and I tried to implement the Jacobi solver for a linear system $Ax=b$. I want to compare the time ...
118 views

### Simultaneously maximize and minimize

I am virtually new to optimization (saw it years ago in a very shallow course) and now I came across a problem that I believe would require from it. The problem is I don't know exactly how to proceed. ...
62 views

### Abaqus, ANSYS, and FVM solver for thermal expansion problem converges to different values

Is it reasonable for a FEM and FVM code to converge to slightly different solutions for the same physical problem (identical BCs, geometry, properties, etc...), provided stability constraints are ...
49 views

### Reverse automatic differentiation and integration

In Symplectic Runge-Kutta schemes for adjoint equations, automatic differentiation, optimal control and more Sanz Serna writes: It is well known that the reverse mode of differentiation implies ...
308 views

### (FEM) 1D time-dependent heat equation convergence problem

I'm simulating a simple 3-node bar with convection BCs at the edges to validate my FEM code. The following data was used: Initial temperature = 25 ºC Temperature surrounding the rod = 10 ºC Thermal ...
86 views

### Optimality of block-Jacobi preconditioner

For a dense $N \times N$ matrix $A$, is the block-Jacobi preconditioner comprising the inverse of the diagonal blocks of $A$ the optimal block-diagonal preconditioner? Could there exist another matrix ...
47 views

### Kinetic preconditioning

Publication arXiv:0804.2583 describes a method for doing self-consistent iteration without having to diagonalize the Hamiltonian operator at every step. IX. PRECONDITIONING As already ...
106 views

### Interpolation vs. Neural network

I am seeking knowledge from the community. I am solving a transport PDE (conservation of solute mass) using COMSOL. At each Newton-Raphson iteration, I need to update a constant called $Kd$ for some ...
27 views

### A preconditioner for self-consistent iteration

I tried to derive a preconditioner for self-consistent iteration similar to section IX in arXiv:0804.2583. For simplicity, consider here only one orbital (one or two electrons) systems. Suppose that ...
37 views

### maximum eigenvalue across subsamples

I have an $N$-dimensional vector of data, say $X_{t}$, with $1 \leq t \leq T$. Of this vector $X_{t}$, I want to consider vectors, say $X_{t}^{b}$, which are $m$-dimensional combinations of elements ...
89 views

### Library for Discontinuous Galerkin method: FEniCS vs deal.ii

I am aware that both FEniCS and deal.ii are capable of solving problems with Discontinuous Galerkin (DG) method. I would like to specifically know if any of these two softwares can cater these ...
28 views

### how to estimate the number of people on a street within an hour?

I tried to use opencv to analyze a video filmed on the street. But the problem is the performance is not enough. I think the number of people must follow the poisson distribution. So I want to ...
42 views

### Find shift in high resolution noisy signal if only local argmax data are available

Let's say I have a signal which consists several pulses of approximately equal height, and I have to correlate it with the expected positions of the peaks to find the shift of this signal w.r.t. a ...
70 views

### Algebraic multigrid for coupled equations

As far as I understand is algebraic multigrid(AMG) a method that was intentionally developed to solve linear systems where every grid point or node has a single DOF. When AMG should now be used for ...
I need to compute repeatedly a function that depends on an integral. The integral is not solvable analytically, but it depends on the argument of the function parametrically, like this:  f(x) = \...